1. Field of the Invention
The present invention is directed to a torsional vibration damper having transmission elements rotatable relative to one another by deflection of coupling bodies which are displaceable along guide paths in both the circumferential and radial directions.
2. Description of the Related Art
German reference DE 41 28 868 is directed to a torsional vibration damper having a drive-side transmission element and a driven-side transmission element which is rotatable relative to the drive-side transmission element against the action of a damping device. The damping device serves to transmit torque between the two transmission elements. The damping device has springs which are guided, via sliding blocks, along a guide path extending in the circumferential direction and which serve as displaceable coupling bodies. A plurality of these springs form a spring set which is in a working connection with one of the transmission elements at one end and with the other transmission element at the other end. Therefore, a deflection of one of the transmission elements in the circumferential direction by a relative movement of the coupling body results in a deflection of the other transmission element.
Torsional vibration dampers according to the above-mentioned reference are suitable for filtering a wide frequency range, that is, for damping amplitudes of different orders. However, particularly troublesome amplitudes of a certain order cannot be effectively suppressed in the manner that is often required.
By constructing the coupling bodies as springs, it is ensured that the two transmission elements will be moved back into their initial positions after every relative deflection brought about by a torsional vibration. Thus, the two transmission elements have an exactly defined reference position relative to one another in the unloaded state. However, a disadvantage in such coupling bodies is that the inertia, which the corresponding transmission element produces in opposition to an introduced torsional vibration, is not changeable. Further, the constructional design of a torsional vibration damper of this type is relatively complicated, since control elements must be provided for the springs at both flywheel masses, the springs acting between these control elements.
A transmission element in the form of a flywheel mass is known from U.S. Pat. No. 5,295,411, in which a circular compensating flywheel mass is received in each of a plurality of circular cavities, wherein the diameter of the compensating flywheel mass is smaller than that of the cavity. A flywheel mass of this type is commonly referred to as a Salomon or Solomon damper and has the advantage that the compensating flywheel masses deflection velocities are dependent on changes in the rate of rotation at the flywheel mass. With a flywheel mass of this kind, torsional vibrations of a determined order, preferably of the second order in four-cylinder internal combustion engines, can be reduced by a determined amount at defined amplitude values. Disadvantageously, however, it is not possible to influence vibrations of another order. Further, wear can result in the running area of the compensating flywheel mass in the cavity or recess because of the linear, and therefore small, contact zone with the respective compensating flywheel mass. Therefore, the recess and compensating flywheel mass become deformed. This in turn negatively influences the deflection behavior of the compensating flywheel mass and accordingly the damper behavior of the flywheel mass. U.S. Pat. No. 2,205,401 shows another damper in which a flywheel mass, having guide paths for damper masses which are in a working connection with an actuating or adjusting device, is fastened to a drive, for example, a crankshaft. The damper masses, as well as the guide paths associated therewith, have a curvature, preferably in a circular shape. The radius of curvature of the damper masses is smaller than that of the associated guide paths so as to enable a rolling movement of the damper masses in the guide paths when torsional vibrations are introduced via the flywheel mass. The plurality of guide paths and the adjusting device mentioned above enable the damper masses to be brought, during an adjusting process by the adjusting device, into the respective guide path required for damping a torsional vibration of a determined order occurring precisely at that time. In contrast to the damper of U.S. Pat. No. 5,295,411, not just one order, but a number of orders can be reduced by a determined amount. Nevertheless, it is not possible to influence torsional vibrations of other orders. Furthermore, the problem of wear at the guide paths, discussed above, also exists.